The Magic Tricycle (horrible name) concept is designed around a reasonable idea. On the highway, you may want to drive a car. So the Magic Tricycle (horrible name) road rages through traffic with three wheels. But when you just want to cruise around town, it transforms into motorcycle mode:
The designers claim that the top wheel adds stability to the 2-wheel mode, but we're not absolutely certain that we'd want more weight so high on the bike (then again, we're not engineers for a reason). And either way, it's a pretty neat idea—one the will lead many of us to promise, "No honey, we won't drive the car in motorcycle mode, we just always really wanted a three-wheeler..."